Subadditivity is a related term of subadditive.
As a noun subadditivity
is (uncountable) the state of being subadditive.
As an adjective subadditive is
(of a function) such that the image of a sum is at most the sum of the images of the summands.
(uncountable) The state of being subadditive.
The statement that a function is subadditive.
(of a function) Such that the image of a sum is at most the sum of the images of the summands.
- The square-root function is subadditive under addition because .